Tire/wheel assembly and run-flat support member

ABSTRACT

A tire/wheel assembly comprising a wheel having a rim, a pneumatic tire mounted on the rim of the wheel and a run-flat support member disposed in the cavity of the pneumatic tire. The run-flat support member includes an annular shell and elastic rings. The annular shell has a support surface located radially outward and two leg portions formed radially inward in a straddling state. The elastic rings support the leg portions on the rim. The annular shell is configured such that an annular cavity portion surrounded by the run-flat support member and the pneumatic tire has a cross-sectional area that varies in the circumferential direction of the tire.

TECHNICAL FIELD

The present invention relates to tire/wheel assemblies and run-flatsupport members, and more particularly, to a tire/wheel assembly and arun-flat support member used therefor, in which noise characteristicscan be improved.

TECHNICAL BACKGROUND

In response to demands in the market, there have been proposed manytechnologies which allow a vehicle to urgently travel several hundredskilometers when a pneumatic tire thereof is punctured during traveling.These many proposals include such a technology disclosed in, forexample, Unexamined Japanese Patent Application Publication No.10-297226 that a support member is mounted on a rim in the cavity of apneumatic tire assembled on the rim, and supports the tire whenpunctured to thereby enable run-flat traveling.

The above run-flat support member comprises an annular shell having asupport surface located radially outward and a leg structure in an openstate disposed radially inward, and elastic rings attached to two legportions of the leg structure, and is supported on the rim via theelastic rings. The run-flat support member allows existing wheels andrims to be used without any specific modifications, and can therefore beadvantageously adopted without causing confusions in the market.

Recently, as part of environmental measures, low noise pneumatic tireshas been required. Pneumatic tires cause resonance of the air in thecavity of the pneumatic tire during traveling, which is one of thecauses that increase road noise.

Conventionally, to solve the above problem, in common tire/wheelassemblies having a wheel and a pneumatic tire mounted on the rimthereof, for example, Unexamined Japanese Patent Application PublicationNo. 2001-113902 discloses such a technology that protrusions aredisposed on the rim at predetermined intervals in the tirecircumferential direction to vary the cross-sectional area of the cavitysurrounded by the rim and pneumatic tire in the tire circumferentialdirection, thereby varying the frequency of the air resonance to reduceroad noise due to the air resonance.

However, there have not been proposed any effective noise reductionmeasures with respect to the tire/wheel assembly having theabove-mentioned ran-flat support member, and proposals for improvementtechnologies are desired.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a tire/wheel assemblyand a run-flat support member used therefor, in which road noise of thetire/wheel assembly having the run-flat support member, due to resonanceof the air in the cavity of the pneumatic tire can be reduced.

In order to achieve the above object, a tire/wheel assembly according tothe present invention comprises:

-   a wheel having a rim;-   a pneumatic tire mounted on the rim of the wheel, the pneumatic tire    having a cavity; and-   a run-flat support member disposed in the cavity of the pneumatic    tire, the run-flat support member having an annular shell and    elastic rings, the annular shell comprising a support surface    located radially outward and two leg portions formed radially inward    in a straddling state, the elastic rings supporting the leg portions    on the rim,-   wherein the annular shell is configured such that an annular cavity    portion surrounded by the run-flat support member and the pneumatic    tire has a cross-sectional area that varies in a circumferential    direction of the tire.

A run-flat support member used for the above tire/wheel assembly of thepresent invention, which is to be disposed in a cavity of a pneumatictire mounted on a rim of a wheel, comprises:

-   an annular shell having a support surface located radially outward    and two leg portions formed radially inward in a straddling state;    and-   elastic rings supporting the leg portions on the rim,-   wherein the annular shell is configured such that, when the run-flat    support member is disposed in the tire cavity, an annular cavity    portion surrounded by the run-flat support member and the pneumatic    tire has a cross-sectional area that varies in a circumferential    direction of the tire.

As described above, the cross-sectional area of the annular cavityportion surrounded by the run-flat support member and pneumatic tirevaries in the tire circumferential direction, thereby allowing thefrequency of air resonance caused in the cavity of the pneumatic tire tovary during traveling of a vehicle. Therefore, road noise due toresonance of the air in the cavity can be improved.

Another tire/wheel assembly according to the present inventioncomprises:

-   a wheel having a rim;-   a pneumatic tire mounted on the rim of the wheel, the pneumatic tire    having a cavity; and-   a run-flat support member disposed in the cavity of the pneumatic    tire in such a manner that the run-flat support member divides the    cavity of the pneumatic tire into an inner cavity part and an outer    cavity part, the run-flat support member having an annular shell and    elastic rings, the annular shell comprising a support surface    located radially outward and two leg portions formed radially inward    in a straddling state, the elastic rings supporting the leg portions    on the rim,-   wherein the annular shell has a plurality of openings through which    the inner cavity part and outer cavity part are communicatingly    connected, the annular shell having regions equally sectioned in a    circumferential direction of the annular shell, the plurality of    openings being unevenly distributed in such a manner that a region    having openings that are maximum in total opening area is 5% to 10%    greater in total opening area than a region having openings that are    minimum in total opening area.

Another run-flat support member used for another tire/wheel assembly ofthe present invention comprises:

-   an annular shell having a support surface located radially outward    and two leg portions formed radially inward in a straddling state;    and-   elastic rings supporting the leg portions on a rim of a wheel,-   wherein the annular shell has a plurality of openings, the annular    shell having regions equally sectioned in a circumferential    direction of the annular shell, the plurality of openings being    unevenly distributed in such a manner that a region having openings    that are maximum in total opening area is 5% to 10% greater in total    opening area than a region having openings that are minimum in total    opening area.

As described above, the uneven distribution of the openings in theequally sectioned regions allows the openings and inner cavity part toact as a Helmholm resonance absorber, thereby absorbing and reducingresonance of the air in the tire cavity during traveling of a vehicle.Accordingly, road noise due to resonance of the air in the cavity of thepneumatic tire can be reduced.

When the pneumatic tire is assembled on the rim, the bead portions ofthe pneumatic tire with the run-flat support member inserted in thecavity thereof are engaged with the rim, and air is then applied toinflate the pneumatic tire, whereby the bead portions are forced toclimb over the humps of the rim to be fitted to the flanges of the rim.According to the present invention, the pneumatic tire can be easilyinflated by air supplied through the openings to the outer cavity partbetween the run-flat support member and the inner surface of thepneumatic tire, thereby allowing the bead portions of the tire to climbover the humps and to be easily fitted to the rim flanges.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view showing a tire/wheel assembly according to anembodiment of the present invention.

FIG. 2A is an enlarged cross-sectional view showing a part in the regionA, C in FIG. 1, taken in a plane that contains the axis of rotation ofthe tire.

FIG. 2B is an enlarged cross-sectional view showing apart in the regionB, D in FIG. 1, taken in a plane that contains the axis of rotation ofthe tire.

FIGS. 3A and 3B illustrate a tire/wheel assembly according to analternative embodiment of the present invention, in which FIG. 3A is anenlarged cross-sectional view corresponding to FIG. 2A, and FIG. 3B isan enlarged cross-sectional view corresponding to FIG. 2B.

FIG. 4 is an enlarged cross-sectional view showing a main part of atire/wheel assembly according to another alternative embodiment of thepresent invention, taken in a plane that contains the axis of rotationof the tire.

FIG. 5 is a partial enlarged fragmentary perspective view showing a mainpart of the run-flat support member in FIG. 4.

BEST MODES FOR CARRYING OUT THE INVENTION

According to the present invention, the run-flat support member isformed as an annular member to be inserted into the cavity of apneumatic tire. This run-flat member is formed to have an outer diametersmaller than the inner diameter of the cavity of a pneumatic tire so asto maintain a constant distance from the inner surface of the cavity,and is formed to have an inner diameter which is substantially equal insize to the inner diameter of the bead portions of a pneumatic tire. Therun-flat support member is inserted into a pneumatic tire, and mountedon the rim of a wheel together with the pneumatic tire to form atire/wheel assembly. The tire/wheel assembly is mounted on a vehicle,and when the pneumatic tire is punctured during traveling, the puncturedtire is supported by the radially outer surface of the run-flat supportmember to thereby allow for run-flat traveling.

The above-mentioned run-flat support member includes an annular sell andelastic rings as main parts.

The annular shell has a continuous support surface formed radiallyoutward for supporting a punctured tire, and left and right sidewalls astwo leg portions in a straddling shape disposed radially inward. Theradially outward support surface is formed so as to have radiallyoutwardly convexed and curved surface sections in a cross-sectionalshape taken along a plane orthogonal to the circumferential directionthereof. The number of the convexly curved surface sections which arearranged in an axial direction of the tire may be one, but preferably,two or more. Formation of the support surface in such a way as toarrange two or more convexly curved surface sections provides thesupport surface with two or more dispersed contact areas with respect tothe inner surface of the tire to thereby reduce localized wear on thetire inner surface, and therefore, the run-flat traveling distance canbe extended.

The elastic rings are attached to the ends of the two leg portionsformed in a straddling state on the radially inner side of the annularshell, respectively, and come into engagement with left and right rimseats to thereby support the annular shell. The elastic rings are formedof rubber or elastic resin, and not only mitigate the vibration andimpact of the annular shell receiving from the punctured tire, but alsoprevent slipping with respect to the rim seats to stably support theannular shell.

The annular shell is formed of a rigid material since the run-flatsupport member has to support a vehicle weight through the puncturedtire. Constituent materials used for the rigid material include metals,resins and the like. The metals may include, for example, steel andaluminum. The resins may include thermoplastic resins and thermosettingresins. The thermoplastic resins may include nylon, polyester,polyethylene, polypropylene, polystyrene, polyphenylene sulfide, ABS andthe like, and the thermosetting resins may include epoxy resin,unsaturated polyester resin, etc. The resins may be used alone or mixedwith reinforcing fibers as fiber-reinforced resins.

The rubber or elastic resin used to constitute the elastic rings may beany kind of rubber or elastic rein if the annular shell can stably besupported. The rubber may be, for example, natural rubber, isoprenerubber, styrene-butadiene rubber, butadiene rubber, or butyl rubber, andthe elastic resin may be, for example, resin foam such as foamedpolyurethane.

The run-flat support member used for the tire/wheel assembly of thepresent invention is premised on the structure described above.

Embodiments of the present invention will be described in detail belowwith reference to the drawings.

Referring to FIGS. 1 and 2, there is shown a tire/wheel assemblyaccording to an embodiment of the present invention, in which referencecharacter X denotes a tire/wheel assembly, reference numeral 1 denotes awheel, reference numeral 2 denotes a pneumatic tire, and referencenumeral 3 denotes a run-flat support member. The wheel 1, pneumatic tire2, and run-flat support member 3 are arranged in coaxial alignment witheach other with respect to the axis of rotation of the wheel to be inthe form of an annulus, which has an arrangement such that the run-flatsupport member 3 is placed in the cavity 2A of the pneumatic tire 2mounted on the rim 1A of the wheel 1.

The run-flat support member 3 comprises an annular shell 4 formed of arigid material such as metal or rein, and left and right elastic rings 5formed of an elastic material such as rubber or elastic resin.

The annular shell 4 includes a support portion 6 comprising two supportsections 6A each of which has a convexly curved support surface 6 aformed radially outward, and a connection section 6B connecting the twosupport sections in the widthwise direction of the shell. The supportsurfaces 6 a are spaced apart from the inner surface 2 a of thepneumatic tire 2 when the pneumatic tire 2 is under a normal condition,and when punctured, the support surfaces 6 a support the punctured tire.The annular shell 4 also includes two side walls which are connected tothe support portion 6 and are formed as leg portions 7 that straddleradally inward, and the elastic rings 5 are attached to the radiallyinner sides of the leg portions 7.

The two leg portions 7 have four regions A, B, C and D equally sectionedin the circumferential direction of the shell. In each of the regions Aand C opposite to each other, the two leg portions includecross-sectionally arc-shaped depressions 7A which are depressed inwardlyand extend circumferentially, as shown in FIG. 2A, and in each of theregions B and D opposite to each other, the two leg portions includecross-sectionally arc-shaped protrusions 7B which protrude outwardly andextend circumferentially, as shown in FIG. 2B. Thus the cross-sectionalshape of each leg portion 7 varies periodically in the tirecircumferential direction, whereby the cross-sectional area of anannular cavity portion 2Aa surrounded by the run-flat support member 3and pneumatic tire 2 varies periodically in regular periods in the tirecircumferential direction.

The annular shell 4 having leg portions 7 described above can easily beobtained by forming shell pieces divided according to the respectiveregions, and jointing the shell pieces by welding or the like.

The run-flat support member 3 having the annular shell 4 constructed asdescribed above is inserted inside the pneumatic tire 2, and the elasticrings 5 are mounted on the rim seats 1 a of the rim 1A together with thebead portions 2 b of the pneumatic tire 2.

According to the tire/wheel assembly X of the present inventionmentioned above, the cross-sectional area of the annular cavity portion2Aa surrounded by the run-flat support member 3 and pneumatic tire 2varies in the tire circumferential direction, thereby allowing thefrequency of air resonance caused in the cavity 2A to vary duringtraveling of a vehicle. Accordingly, road noise due to resonance of theair in the cavity 2A can be reduced.

Referring to FIGS. 3A and 3B, there is shown an alternative embodimentof a tire/wheel assembly according to the present invention. Thistire/wheel assembly X′ has the following structure in theabove-mentioned tire/wheel assembly X, instead of providing the legportions 7 with the depressions 7A and protrusions 7B. The connectionsection 6B connecting the support surfaces 6 a is formed to havecircularly curved depressions which are depressed deeply inwardly in theregions A and B as shown in FIG. 3A, and is formed to have circularlycurved protrusions which protrude outwardly in the regions B and D asshown in FIG. 3B, whereby the cross-sectional shape of the connectionsection 6B varies periodically in the tire circumferential direction.

This also causes the cross-sectional area of the annular cavity portion2Aa surrounded by the run-flat support member 3 and pneumatic tire 2 tovary in the tire circumferential direction, whereby the same effectmentioned above can be obtained.

In the embodiments of the present invention set forth hereinabove, whenthe cross-sectional area of the cavity portion 2Aa varies as statedsupra, it is preferable that the cross-sectional area of the cavityportion 2Aa vary such that the maximum cross-sectional area thereof is2% greater or more than the minimum cross-sectional area thereof. In theembodiments shown in the drawings, the maximum cross-sectional areaexists in each of the regions A and C, and the minimum cross-sectionalarea exists in each of the regions B and D. The cross-sectional area ofthe cavity portion 2Aa in each of the regions A and C is 2% greater ormore than the cross-sectional area thereof in each of the regions B andD. If the difference therebetween is less than 2%, it is difficult toeffectively vary air resonance frequency. It is more preferable that thedifference be 5% greater or more. The upper limit of the difference ispreferably 20% or less in terms of workability of the annular shell 4.

It is preferable that the forgoing annular shell 4 be formed by formingshell pieces divided in the shell circumferential direction according tothe respective regions, and jointing the shell pieces by welding or thelike to easily produce the annular shell, as described above, but it isnot limited thereto as is obvious. The annular shell 4 may be, forexample, integrally formed.

In case where the annular shell 4 is formed by jointing the shell piecesas mentioned above, there exist steps in the joint parts havingdepression and protrusion portions, whereby the annular shell 4 havejoint gaps through which the outside and inside of the annular shell 4are in communication with each other. The joint gaps may be left as theyare, or may be closed using other materials. Preferably, the joint gapsare closed, thereby contributing to slightly decreasing road noise.

The annular shell 4 may be constructed such that the shell pieces areformed to have no depressions or protrusions at opposing end thereof,and are jointed without making steps.

In the above embodiments, there are exemplified the annular shell 4 inwhich only the cross-sectional shapes of the leg portions 7 vary, or theannular shell 4 in which only the cross-sectional shape of theconnection section 6B varies. However, the annular shell 4 may have acombination of these features. For example, the annular shell 4 may beconstructed so as to have a cross-sectional shape shown in FIG. 3A inthe region A, a cross-sectional shape shown in FIG. 3B in the region B,a cross-sectional shape shown in FIG. 2A in the region C, and across-sectional shape shown in FIG. 2B in the region D.

The annular shell 4 may also be constructed such that the leg portions 7and connection section 6B are provided with the depressions andprotrusions stated supra, whereby the cross-sectional area of the cavityportion 2Aa surrounded by the annular shell 4 and pneumatic tire 2varies in the tire circumferential direction.

In the embodiment shown in FIGS. 2A and 2B, the two leg portions 7 areprovided with the depressions 7A and protrusions 7B. However, either ofthe two leg portions 7 may be provided therewith, and the annular shell4 may have a combination thereof.

It is preferable in terms of effectiveness that the cross-sectional areaof the cavity portion 2Aa varies periodically as described above.However, it is not limited thereto, and the cross-sectional area of thecavity portion 2Aa may randomly vary in irregular periods.

When the cross-sectional area of the cavity portion 2Aa variesperiodically, it is preferable to have two periods. In this case, asshown in the above embodiments of FIGS. 2 and 3, the annular shell ispreferably configured to vary in two periods in the order of the maximumcross-sectional area region, minimum cross-sectional region, maximumcross-sectional area region and minimum cross-sectional area region.

The depressions 7A and protrusions 7B of the leg portions 7 arepreferably in the forms of circular arcs in cross section as describedabove in terms of supporting load during run-flat traveling, but ifthere are no obstacles to run-flat traveling, any of shapes may beemployed. The same goes for the connection section 6B shown in FIGS. 3Aand 3B.

Referring to FIG. 4, there is shown another alternative embodiment of atire/wheel assembly according to the present invention. This tire/wheelassembly Y is constructed such that the annular shell 4 has nodepressions or protrusions but a plurality of openings 8 formed in thetwo leg portions 7 as shown in FIG. 5. The hermetically-closed innercavity part 2A1 and hermetically-closed outer cavity part 2A2 of thecavity 2A defined by the run-flat support member 3 placed in the cavity2A of the pneumatic tire 2 are communicatingly connected through theopenings 8.

In the embodiment shown in the drawings, the annular shell 4 has fourregions A, B, C and D equally sectioned in the circumferential directionthereof. The total opening area, on the outer surface 4 a of the annularshell 4, of openings 8 in each of the regions A and C is maximized, andthe total opening area of openings 8 in each of the regions B and D isminimized. The maximum opening area regions A and C and the minimumopening area regions B and D are alternately placed, and the pluralityof openings 8 are unevenly distributed such that the regions haveopenings 8 that are different in total opening area. The regions A and Chaving the maximum total opening area of openings 8 are 5% to 10%greater in total opening area than the regions B and D having theminimum total opening area of openings 8.

According to the tire/wheel assembly Y, the uneven distribution of theopenings 8 in the equally sectioned regions A, B, C, and D allows theopenings 8 and inner cavity part 2A1 to act as a Helmholm resonanceabsorber, thereby absorbing and reducing resonance of the air in thetire cavity 2A during traveling of a vehicle. Accordingly, road noisedue to resonance of the air in the cavity 2A of the pneumatic tire 2 canbe improved.

When the pneumatic tire 2 is mounted on the rim, the pneumatic tire 2can be easily inflated by air supplied to the outer cavity part 2A2 ofthe pneumatic tire 2 through the openings 8, thereby allowing the beadportions 2B of the tire to climb over humps 1 b and to be easily fittedto the rim 1A. Accordingly, workability of assembling the tire on therim can be improved.

If the difference between the total opening area of openings 8 in themaximum total opening area region A, C and the total opening area ofopenings 8 in the minimum total opening area region B, D is less than5%, it is difficult to provide an effectively absorbing function. If thedifference is more than 10%, the mass of the run-flat support member 3varies noticeably around the circumference thereof, whereby vibration isapt to occur to thereby badly affect ride comfort.

It is preferable, in terms of obtaining the highest noise reductioneffect, that the uneven distribution of the openings 8 be arranged suchthat the regions A and C having the maximum total opening area and theregions B and D having the minimum total opening area are alternatelyplaced, as described above, to have two periods, but it is not limitedthereto. The annular shell 4 may be arranged such that the annular shell4 has two to seven regions equally sectioned in the circumferentialdirection thereof and a region having openings 8 that are maximum intotal opening area is 5% to 10% greater in total opening area than aregion having openings 8 that are minimum in total opening area. If theannular shell has eight or more equally sectioned regions, it is notpreferable because the distribution of the openings 8 is closer to aneven distribution.

The openings 8 are elliptical in shape in the drawing shown, but are notlimited thereto. The openings 8 may be of any shape such as circle,rectangle, square or the like if the openings can communicatinglyconnect the inner cavity part 2A1 and the outer cavity part 2A2.

The opening length of each opening 8 is preferably in the range of 3 mmto 6 mm. The opening length referred herein is as follows. In the caseof an ellipse, a major axis and a minor axis are the opening lengths; inthe case of a circle, a diameter is the opening length; in the case of arectangle, square, etc, the length of a diagonal line passing throughthe center thereof is the opening length. If the opening length is lessthan 3 mm, it is difficult to provide an effectively absorbing function.If the opening length is more than 6 mm, it is not preferable in termsof the strength of the annular shell 4.

The entire opening area of all the openings 8 on the outer surface 4 aof the annular shell 4 is preferably in the range of 0.3% to 6.0% withrespect to the entire area of the outer surface 4 a of the annular shell4. If the entire opening area is less than 0.3%, it is not preferable interms of an absorbing effect. If the entire opening area is more than6.0%, there is a risk of interfering with run-flat traveling because thestrength of the annular shell 4 decreases.

In an annular shell 4 having the above-mentioned openings 8 which areunevenly disposed, the equally sectioned regions are determined asregions sectioned at a position where there exists one region that isthe largest in the total opening area of the openings 8 a when lines bywhich the regions are equally sectioned are displaced from 0 to 360degrees in the circumferential direction of the annular shell.

In the above embodiments, the present invention exemplifies the annularshell 4 having two support surfaces 6 a. However, the number of thesupport surfaces 6 a is not limited to two, but may be one or a pluralnumber which is more than one.

EXAMPLE 1

Prepared were tire/wheel assemblies according to the present inventiontire/wheel assemblies 1 and 2 (present invention assemblies 1 and 2) andconventional tire/wheel assembly 1 (conventional assembly 1), having atire of size 205/55R16 and a rim of size 15×6 1/2JJ, the presentinvention tire/wheel assembly 1 having a construction shown in FIGS. 2Aand 2B in which the leg portions of the annular shell had depressionsand protrusions, the present invention tire/wheel assembly 2 having aconstruction shown in FIGS. 3A and 3B in which the connection section ofthe support portion of the annular shell had depressions andprotrusions, the conventional tire/wheel assembly 1 having the sameconstruction as the present invention tire/wheel assembly 1 except thatthe leg portions of the annular shell had no depressions or protrusions.

In the present invention tire/wheel assemblies 1 and 2, the maximumcross-sectional area of the cavity portion is 4% greater than theminimum cross-sectional area thereof.

The test tire/wheel assemblies were mounted on a passenger car of 2.5liter displacement with the air pressure thereof being 200 kPa, andevaluation testing for road noise was conducted according to thefollowing method. The results shown in Table 1 were obtained.

Road Noise

In a dry road test course, noise was measured in the car when the carwas run straight at a speed of 50 km/h. The partial overall values in afrequency range of 100 Hz to 500 Hz were used to compare with eachother. The results were represented on the basis of the conventionaltire/wheel assembly 1 as standard. The smaller the value, the lower theroad noise, and noise characteristics are better.

TABLE 1 Conventional Present Invention Present Invention Assembly 1Assembly 1 Assembly 2 Road Noise Standard −1.1 dB −1.3 dB

As can be seen from Table 1, the tire/wheel assemblies of the presentinvention can reduce road noise due to resonance of the air in thecavity of the pneumatic tire.

EXAMPLE 2

Prepared were tire/wheel assemblies according to the present inventiontire/wheel assemblies 3 to 5 (present invention assemblies 3 to 5),comparison tire/wheel assemblies 1 and 2 (comparison assemblies 1 and 2)and conventional tire/wheel assembly 2 (conventional assembly 2), havingthe same sized tire and the same sized rim as in Example 1, the presentinvention tire/wheel assemblies 3 to 5 and comparison tire/wheelassemblies 1 and 2 each having a construction shown in FIG. 4 in whichthe difference between the maximum total opening area and minimum totalopening area of openings in four equally sectioned regions of theannular shell was arranged as shown in Table 2, the conventionaltire/wheel assembly 2 having an annular shell with no openings.

The present invention tire/wheel assemblies 3 to 5 and comparisontire/wheel assemblies 1 and 2 had the same entire opening area of allthe openings that was 0.5% with respect to the outer surface area of theannular shell.

The test tire/wheel assemblies were mounted on a passenger car of 2.5liter displacement with the air pressure thereof being 200 kPa.Evaluation testing for road noise was conducted in the method shown inExample 1, and evaluation testing for ride comfort was conducted in thefollowing method. The results shown in Table 2 were obtained.

Ride Comfort

Feeling testing was conducted by a test driver in a dry road testcourse, and the testing results were evaluated by 5 levels. The greaterthe value, the better the ride comfort.

TABLE 2 Road Ride Difference (%) Noise Comfort Conventional Assembly 2 —Standard 3 Comparison Assembly 1 3 −0.1 dB 3 Present Invention 5 −0.9 dB3 Assembly 3 Present Invention 7 −1.1 dB 3 Assembly 4 Present Invention10 −1.2 dB 3 Assembly 5 Comparison Assembly 2 15 −1.2 dB 2.5

As can be seen from Table 2, the tire/wheel assemblies of the presentinvention can effectively reduce road noise while maintaining ridecomfort.

INDUSTRIAL APPLICABILITY

The tire/wheel assembly of the present invention having theaforementioned excellent effects can be very effectively utilized as atire/wheel assembly which is to be mounted on a vehicle and allows forrun-flat traveling.

1. A tire/wheel assembly comprising: a wheel having a rim; a pneumatictire mounted on the rim of the wheel, the pneumatic tire having acavity; and a run-flat support member disposed in the cavity of thepneumatic tire, the run-flat support member having an annular shell andelastic rings, the annular shell comprising a support surface locatedradially outward and two leg portions formed radially inward in astraddling state, the elastic rings supporting the leg portions on therim, wherein the annular shell is configured such that an annular cavityportion surrounded by the run-flat support member and the pneumatic tirehas a cross-sectional area that varies in a circumferential direction ofthe assembly due to changes in the shape of the annular shell in thecircumferential direction in a non-running condition.
 2. A tire/wheelassembly according to claim 1, wherein the cross-sectional area of theannular cavity portion varies in such a manner that a maximumcross-sectional area thereof is 2% greater or more than a minimumcross-sectional area thereof.
 3. A tire/wheel assembly according toclaim 1, wherein the cross-sectional area of the annular cavity portionvaries periodically.
 4. A tire/wheel assembly according to claim 1,wherein the leg portions of the annular shell have a cross-sectionalshape which varies in the tire circumferential direction.
 5. Atire/wheel assembly according to claim 1, wherein the annular shell hassupport surfaces connected via a connection section, the connectionsection having a cross-sectional shape which varies in the tirecircumferential direction.
 6. A tire/wheel assembly according to claim1, wherein the annular shell is formed by joining a plurality of shellpieces into which the annular shell is divided in a circumferentialdirection of the shell.
 7. A run-flat support member which is to bedisposed in a cavity of a pneumatic tire mounted on a rim of a wheel,comprising: an annular shell having a support surface located radiallyoutward and two leg portions formed radially inward in a straddlingstate; and elastic rings supporting the leg portions on the rim, whereinthe annular shell is configured such that, when the run-flat supportmember is disposed in the tire cavity in a non-running condition, anannular cavity portion surrounded by the run-flat support member and thepneumatic tire has a cross-sectional area that varies in acircumferential direction of the member due to changes in the shape ofthe annular shell in the circumferential direction.
 8. A run-flatsupport member according to claim 7, wherein the cross-sectional area ofthe annular cavity portion varies in such a manner that a maximumcross-sectional area thereof is 2% greater or more than a minimumcross-sectional area thereof.
 9. A run-flat support member according toclaim 7, wherein the cross-sectional area of the annular cavity portionvaries periodically.